Last spring Tesla CEO Elon Musk debuted his company’s Powerwall home battery pack, a rechargeable store for solar energy. Since then the company has been cooking up a second generation of the device.

At a Paris event on Friday, Musk told Tesla (tsla) customers that the next iteration of the company’s wall-mounted source of backup power is due out as early as this summer, as the autos and energy blog Electrekfirst reported.

“We’ve got the Tesla Powerwall and Powerpack, which have a lot of trials underway right now around the world. We’ve seen very good results,” said Musk, who also heads the aerospace startup SpaceX and serves as chairman of solar energy firm SolarCity (scty). “We’ll be coming out with version two of the Powerwall probably around July or August this year, which will see further step change in capabilities.”

(You can watch the video of the PayPal (pypl) co-founder’s speech below. Skip to time 9:00 for his Powerwall comments.)

Tesla’s original residential lithium-ion battery weighs 220 pounds, comes with a 10-year warranty, and comes in two sizes: 7 kilowatt-hour ($3,000) or 10 kilowatt-hour ($3,5000). The packs sold out in 2016, and the company began assembling them in its Gigafactory—its manufacturing plant based outside Reno, Nev.—last fall.

No word yet on the new product’s specs though. Reached for comment, Tesla spokesperson Khobi Brooklyn confirmed Musk’s comments, and told Fortune, “We don’t have any additional details to share at the moment.”

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